Semi-automatic telephone system.



H. W. MUNSELL.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATON FILED SEPT. 25, |915.

Patented Mar. 4

H. w. n/IUNSELL.`

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION man sEPLzs. 1915.

1,296,104. Patemd Ma1-.4,1919.

2 SHEETS-SHEET 2.

i La@ I E; Biffi i manna* otros.

HARRY w. NUNsELL, or INDIANAPOLIS, INDIANA, AssIGNOR To KELLOaeswrrcI-I BOARD AND SUPPLY4 COMPANY, or cHIcAGfO, ILLINOIS, A CORPORATION or ILLINOIS.

Sp'ecOation'Of Letters Patent.

ratentearrat. A, iam.

*- Application le September 25, 1915. v Serial No. 52,542..

To all whom t may concern:

Be it known that I, HARRY W. MUNSELL,

a citizen of Ithe United States of America, residing in Indianapolis, county of Marion,

tems of the semi-automatic type in which an operator is employed to transmit impulses to operate switches to select the contacts of a called line in an automatic exchange. In

.systems of this character a great many connections are put through by an operator, so it is desirable to have a device which is easy of manipulation and quick in operation. To this end I employ a series of impulse control keys equal in number to the number of subsribers that the final selector or connector switch has access to. By this arrangement it is only necessary' to operate one key to call any subscriber in the exchange. v

One of the features of my invention is the provision of a calling device of the character above described, that may readily be associated with any trunk of a plurality of trunks extending to the final selectors or connectors that are used to establish connection with called subscribers lines, and the provision' of means for preventing the impulse lead of the calling device from being operatively associated with more than one of -said connectors at a time.

In general, the object of my invention is the provision of an impulse sender of the larly point out the features thereof.

I preferably arrange the subscribers lines in groups of any desirable size. A plurality of final selectors-or connectors are associated with each group of lines and the trunk lines connected to these connectors terminate in their oppositeI ends, in multiple jacks upon an operators board, each of the trunk lines being accessible to a plurality of operators.

. Each operator thus has a plurality of groups I lines.

of jacks appearing before her equal in number to the number of groups oflsubscribers7 For a more complete understanding of my invention reference may be had tothe accompanying drawings which consist of Figure l, Part l, and Fig. l, Part 2. When Fig. l Part 1 is placed to the left of Fig. 1 Part 2, the two parts thus placed illustrate a. complete circuit arrangement-betwee'n a calling and a called subscriber. Fig. 2 is a view of a strip of impulse keys associated with the impulsemachine of my invention.

Referring now more in general to my invention, as illustrated in the accompanying drawings, and referring to Fig. 1 Part l, at the left `of said drawing I show a well-known substation A terminating at the exchange in a line circuit L comprising a line relay LR, a cut-ofi' relay CO, a line lamp S and the multiple jacks J. The cord circuit B comprises an Vanswering plug AP and a calling plug CP, the said plugs being connected by the heavily marked conductors and having local subscriber, when the cord circuit B is used for interconnecting two local subscribers. An order-wire key OW is associated with cord circuits B which when depressed connects the operators set O of the cord circuit B with the operators set O1 which is associated with the trunk circuit C.

The trunk circuit C at its incoming end terminates in a trunk jack TJ and at its outgoing end in a trunk plug TP the said plug 4 and Jack being connected through a repeating coil RC by the heavily marked conductors, which have condensers K2 and K3, interposed between the windings l, 3 and 2, 4 of the repeating coil RC. The trunk circuit C is provided with a trunk calling sleeve supervisory relay TC energized when the operator of cord circuit B plugs into the assigned trunk jack TJ. A ringing signal relay RS is provided which is energized when any one of the plungers 0f the ringing key RKlv is depressed. A combined interrupter which is energized when the relay-RS is operated. An impulse guard relay GR is also lli provided to guard against interference-on the impulse wire when a connection i s being set up while the impulse machine 1s' running. The operation of this relay w1ll be more fully described in the following description of the operation of the system. A sleeve relay SR is provided which is operated when the connector E has seized the called line as does also the interruptor connector relay IN which connects the interrupter l, to intermittently energize and deenergize the relay IC to connect the rlnglng lead to supply ringing current to the called line. A tlp relay TR is provided which is energized when the called subscriber answers to' disconnect ringing current and also ed'ace the supervisory signal 27. v

The circuit of the impulse machine as illustrated at D in Fig. 1,',Part l, comprises a plurality of keys K diagrammatically illustrated at D and shown in detail in Fig. 2. These keys K are mounted in the key shelf of the switchboard before an operator. l provide one key for each bank contact 6 on the impulse machine. When an one of a plurality of theseJ keys is depresse an energizing circuit for the operating relay 0R is established which in turn operates motor magnet MM. Motor magnet im@ steps the wiper W of the impulse machine over the contacts 6 associated with the said impulse machine until the contact associated with the depressed key is engaged when the impulse machine comes to rest. The impulses are thus transmitted to operate the connector switch E at the automatic exchange to select the contacts of the called line. A release magnet RM3 and a key release magnet KM are provided, the magnet RM3 upon-A energizing releases the actuated wiper of the impulse machine and the magnet KM upon energizing, releases any one of the keys which 4has been depressed. The construction of the key K as illustrated in Fig. 2

' will be more fully described in the ensuing specification. -O-normal contacts ON are provided which assume their alternate position upon the first step of the wiper W from normal position.

rlhe `connector switch E is of the wellknown type and terminates at one end in a trunk jack TJ1 before a trunk operator and at its other end at the automatic exchange in wipers 7, 8, and 9, said wipers being associated with the connector contacts 10, 11, 12. The connector switch as shown is preferably a one motion switch, that is, it has rotary motion only. The switch is provided with the usual switch shaft (not shown) carrying the wipers 7, 8 and 9. I also show the side switches a, b, o and a? which assume their second position when the contacts maar@ of the called line have been seized by the connector switch E. A rimary relay PR anda primary magnet P supply the motive power to step the wipers 7, 8, and 9 over the bank contacts l0, 11 and 12, into engagement with the contacts of the called line. A side switch relay SW is provided to sume their alternate position upon the rst stepof the wipers 7, 8, 9 from normal.

To the right of Fig. 1, Part 2,'l show a calling substation G provided with the usual apparatus and also lincluding'a calling device CD. The station G terminates in an sociated with'the connector switch E and asautomatic line circuit lF which includes a line relay LRl and a cut-od' relay C01.

Having described in general the apparatus embodying my invention, l will now describe in detail the operation of my system as illustrated.

Assuming now that the subscribpr at the substation A wishes to initiate a call, the

subscriber thereat removes his receiver,

`which act closes an energizing circuit for the relay'LR of the line circuit L, to light the line signal S. The operator associated with the cord circuit B, noting the lighted signal S inserts the answering plug A? of cord B into the jack J of the calling line and throws her listening key LK to connect her operators set 0 to the cord conductors to inquire the wants of the calling subscriber. Upon the insertion of the answering plug AP into the jack J, a series energizing circuit for the cut-oli'l relay CO and the sleeve supervisory relay AS is established traced from battery through the winding of the relay AS, the sleeve contacts of the connected plug andfjack and through the winding of the relay CO to ground. The relay CO operating opens the circuit yof the line relay LR; the said line relay restoring, brings about the4 eiiacement of the line signal S. The answering tip supervisory relay 'AT is also energized through the now closed contacts of the cut-ofi' relay CO, and through the `substation back to battery. The operation-of the relay AT prevents the premature Ilighting of the supervisory signal SS. Aummg that the subscriber at substation A wishes to converse with the subscriber at a distantautomatic exchange, and assuming further that it is the substation G. that is wanted, the operator at B now depresses llO operator after depressing ke OW, repeatsA the number of the called su scriber to the operator of trunk circuit C and the oper` ator at the trunk circuit C then assigns the trunk to be used.

The operator at the cord circuit B now inserts the plug CP into the trunk jack TJ closing a series energizing circuit. for the relay CS of B and the relay TC of the trunk circuit extending from battery through the winding-of the relay CS, the sleeve con'- tacts of the connected plug and jack, the winding 3 of the repeating coil RC and through the lower winding of the relay TC to ground. The closing of alternate contact 200i relay TC establishes a circuit for the signal 21, traced from battery through the said lamp 21, the alternate contact 20 of relay TC to ground at normal contact 22 of relay SR. The lighted signal 2-1 noties theA operator at the trunk circuit C that the i operatorrat B has plugged into the assigned trunkjack. The lampremains glowing until the called subscriber is signaled when it is effaced. The operation of the relay CS of the cord circuit `B closes a circuit through the signal SS1 traced from ground through i normal contact '23 of relay CT, alternate contact 24 of relay CS and through the said supervisory signal SS1 to battery, the lamp remaining glowing until the called subscriber answers.'

. Returning to the operator at C, she first tests the trunk jack TJ1 by placing the tip of the trunk plugTP to .the sleeve of the trunk jack TJ1 and tests-'it as to its idle or busy condition. If the trunk jack tested is busy,

'the operator" will receive the customary click signifying the busy condition of that particular connector. Assuming that the connector E connected to the trunk jack TJ1 is idle, the operator inserts the plug TP into the jackTJ1 and depresses one of the plungers of theringing key RK1 to connect the proper frequency of ringing current to ring the call bell of the called subscriber, and

then depresses the proper impulse key K of tending from battery the impulse machine D, to transmit impulses from the said Vimpulse machineto operate the connector E to extend the connection` to the called subscriber at the substation G. The operator at C- having depressed the plunger of the ringing key to its fully depressed position, anl energizing circuit for the relay RS is established, the circuit eX- through the lower winding of the relay S, the alternate com tact 25 of the depressedringingkey plunger p to ground at normal contact 26 of relay TR. Upon the energization of the relay RS, the circuit for the supervisory signal 27 is established traced from battery through the said signal, alternate contact 28 of relay RS to ground at normal contact 26 of relay TR, the signal remains lighted until-the called subscrlber has answered. A circuit for the relay IC is also established upon the energization of the relay RS,l the circuit being traced from battery, normal contact 29 of relay GR, alternate lcontact 30 of relay RS and through the 'winding of relay IC to ground at normal contact 31 of relay IN. The operator at trunk circuit C having depressed the impulse key K corresponding to the number of the wanted substation, brings about the momentary closure of the contact spring '32 of the depressed key plunger establishing an energizing circuit for the oper a0 ating relay OR of the impulse machine D, said circuit 'being traced from battery through therelay OR, normal contact 33 of the motor magnet M2M, normal contact 34 of the off-normal springs ON to ground at 'a5 the momentarily closed contact 32 of the depressed key plunger K. When the depressed impulse key K is released, it assumes its indicating position,'the circuit 32 again opening. The contact 35 associated with the 90 depressed impulse key K remains open removing ground from the bank contacts associated with the depressed key. The. relay OR, 'upon energizing, closes an energizing circuit for the motor magnet MM traced from battery through the winding of the magnet MM, through alternate contact 36 of rela OR to ground.` The `slow acting relay C is also energized over a circuit traced from battery through the windingof said relay, the alternate contact36 of relay OR to ground. The relay ORhas its circuit interrupted vwhen the contact 32 of' K is opened, when the key assumes its indicating position after pressure is released. The 1mi' alternate contact 38 of relay AC (which being a slow acting relay has not as yet re- 19'5 leased), normal contact 33 of magnet MM and through the winding of relay OR to battery. The motor magnet MM is thus alternately energized and denergized, stepping the wiper WV of the impulse mechanism over the bank contacts 'by means of a suitable ratchet and pawl mechanism as is wellknown. -Wiper W is therefore stepped Aaround until it encounters the ungrounded contact associated with the depressedim 125 pulse key K. The impulses transmitted by the opening and A closing of contact 39 of relay CR are transmitted Jfrom ground at contact. 39 of relay OR, over conductor 4Q, normal contact 41 of' relay IN., 139

' .the alternate contact 42 of relay IC,'the tip contacts of the connected trunk plug TP and jack TJ1, side switch wiper 68, contact 4'3, through the Winding of the primary relay PR of the connector switch E to battery. A resistance R is provided in the impulse circuit D which is cut in when the wiper W takes its first step and as the ott-normal con, tacts assume their alternate position upon the ;rst step of the wiper, so that should an `operator be slow in removing her nger from the depressed impulse key K, when a low number is being called, the switch will not be released and stepped forward again caus in the transmission of false impulses, but wi l remain in its operated position until t-he shunt resistance R is cut out of circuit.

Upon the first energization of the'relayk PR, an energizing circuit for slow acting relay 50 is established, extending from battery through the winding of relay 50 to ground at alternate contact 51 of relay PR. rPhe I normal contact 51 of relay PR.

ergizatio'n of the relay PR an energizing circuit for prlmary magnet PM is established extending from battery through the winding of the magnet PM, conductor 60 and the alternate contact 61 of relay 50 to 'ground at he relay 50 being slow to release, its contact 61 is held energized during the transmission of impulses to the primary magnet PM. The

. impulses, from the impulse machine transmitted to the connecter E, as before described, causes the relay PR to energize and denergize and, due to the opening and closin of its normal contact 51 the said magnet Pll is'likewise energized and denergized Steppin the wipers 7, 8, and 9 of connector switch f into engagement with the contacts 10, 11, and 12 ofthe called line. The relay 50, as before described, being slow acting, is not a'ected by the rapid interruptions of relay PR and therefore the relays 53, 54 remain energized during the transmission of` said im ulses. Upon the first step of the wipers t e off-normal contacts ON1 assume their alternate position. When the wiper W of the impulse machine D engages the ungrounded contact 6, the ground having been removed when its associated key K was depressed by the trunk operator, the circuit for relay OR is interrupted lthereby interrupting the circuit of the magnet MM at contact 36 of 0R. The wiper W comes to rest and he circuit Ylhe relay AC being a y through the Winding 'oRll/li", alternate contact 44 of o-normal contacts 0N, the normal contact 45 ot relay AC to battery. The circuit or magnet KM being traced from ground through the winding of KM, alternate contact 44 and normal contactA 45 to battery. The magnet RM3 releases the wiper W and allows itv to restore and the magnet KM restores the depressed key K rendering available the impulse machine for sending another set of impulses.

rllhe impulses having ceased, the relay PR remains denergized thereby opening the energizing circuit for the relay 50. 'Pherelay 50 restoring opens the circuits of relays 53, 54 at contact 52. rlhe relay 50 denergizing closes a circuit for the side switch magnet SW, extending from battery through the winding of said relay SW, conductor 63, alternate contact 64. or"v -onorma'l contacts 0N1, contact 65 and the wiper 66 to ground at normal contact 67 of relay 50. Upon the energization of the niagnet SW the side switch wipersl 57, 66, 68 and 69 are stepped to their sectond position into engagement with contacts 7 3, 70, 71 and 72. lWhen the side switch wiper 66 leaves its contact 65 and engages the contact 70 the circuit for the magnet SW is opened. The said magnet denergizing, permits the side switch to remain in its second position.A As soon as the side switch has assumed its second position, a series circuit for the relay 74 of the connector E and the sleeve relay SR of the trunk circuit C at the manual exchange is established, said series circuit being traced from ground through the upper winding of the relay 74,'conductor 75, contact 72, wiper 69, the sleeve contacts of the connected jack and plug TJ1 'and TP, conductor 76 and through the winding of the relay SR to battery. rlhe o ening of the normal contact 22 of relay R efaces the signal 21 of the trunk circuit C notifying the operator that the called party is now being rung. The cut-ott relay CO1 of the line circuit F associated with the called subscriber G is also energized, over a circuit traced from ground at normal contact 67 of relay 50, wiper 66, contact 70, the normal Contact 77 of relay 54, wiper 7, contact 10, conductor 78 and through the winding of the cut-0E relay C()1 to battery. The cut-oli relay CO1, upon energizing removes the substation control of the line circuit L1 when the called subscriber answers in response to the call.

Upon the energization of the relay SR `of the trunk circuit C, an energizing circuit for relay IN- is established being traced from battery through the winding of said relay to ground at alternate contact 22 of relay SR. The closing of contact 81 of rela-y IN connects the interruptor I tothe relay IC to intermittently energize and ,deener-A gize the said relay IC. The circuit being traced from ground through the interrupteil I, the alternate contact 79 of relay TC,

.- of the line. The path for the ringing current extending from the ungrounded pole of generator g closed contact of the plunger of the ringing key RK", ringing lead 82, al-

ternate contact 41 of relay TN, conductor 83,

` alternate contact 42 of relay IC, tip contacts of the connected plugI and jack, the wiper 68, contact 71, the normal contact 84 of relay 53, Wiper 8, contact 11, condenser andcall bell or called substation Gr, contact 12 and Wiper 9, normal contact 85 of relay53, the

ringing current dividing at 86 part of it going through the` normal contact-87 t of relay l88 and through the Winding 0f' the relay 89 to battery, part extending through the condenser K5 contact 72 of side switch c upper Winding of the relay 74 to ground, 'and a part extending through the Wiper 69 of side switch c, sleeve contacts of connected plug and jack, conductor 76, through winding ont relay SR of trunk circuit C to battery.' The bell of called substation Gr is thus intermittently operated and when the subscriber at called substation G answers the tip relay TR of trunk circuit C and -relay 89 of the connector switch E are energized in series, said energizing circuit being traced from ground through the 4Winding of said relay TR of trunk circuit C alternate contact 90 of relay SR, normal contact 42 .of relay TC, tip

contacts of the connectedplug and Jack, wiper 68., contact 71, contact 91 of relay` 89,l normal contact 84 of relay 53, wiper 8, contact 11, through the now closed contacts of the switch-hook of the called substation G, returning through contact '12, Wiper 9, normal contact 85 of relay53, normal contact 87 of relay 88 and through the winding ofthe relay 89 to battery. pon the energization of TR of trunk C the circuit for si al 27 isefaced, nati the o erator thiithe subscriber.- has aligvliied. This closure of alternate rcontact 110 of relay TR closes a circuit for relay CT of cord ,B, circuit being traced from ground through the winding of relay C'lclosed contact 111er Vscribers telephone.

relay CS, tip contacts of the plug CP and jack TJ, winding 1 of repeating coil RC, alternate contact 110 of relay TR and through the upper Winding of relay TC to battery. Relay CT u on energizing o ens the circuit of signal 1 of cord B. pon the energization of relay TR the circuit for relay RS is interrupted at contact 26 of relay TR. The relay RS restoring opens contact 30 which opens the circuit for relay IC, which denergizes and disconnects the ringing current. Upon the energization of the relay 89 the circuit for relay 88 is closed` traced from battery through the lower Winding of the relay 88, alternate contact 92 of relay 89 to the sleeve conductor, through the normal contact 85 of relay 53, Wiper 9` contact 12, through the closed contacts of the switch-hook of the station G, contact 11 of the Wiper 8, normal Contact 84, alternate contact 93 of relay 89, and through the upperwinding of relay 88.to ground. The relay 88, furnishes battery for talking purposes to the called sub- The relay 88, upon energizing, closes a substitute circuit for relay 89 said substitutecircuit being traced from battery through the Winding of the said relay 89, alternate Contact 87 and through the'winding or relay 94 to ground. The relay 94 upon energizing opens the release circuit for the connector switch E and prevents the connector switch from releasing until the called subscriber has replaced his receiver upon the switch-hook and the operator has removed the4 plug from the trunk jack which leads to the connector switch E. The energization of relay 88 also closes a .substitute circuit for relay TB of cord circuit C extending from ground through the Winding of the said relay TR, alternate contact 90, normal Contact 42, tip contacts of the connected plug TP and trunk jack T31, Wiper 68, contact 71, the

lconductor 95, alternate c0ntact96 of relay 88 and through the lower Winding of relay 74 to battery. The subscribers may novvV carry on conversation vover the' heavily marked circuit.

Assuming now that the subscribers have finished conversation, they replace their receivers upon their respective switch-hooks. The re lacing of the receiver at the called substatlon G opens the energizing circuit for relay 88. The said relay restoring opens the energizin circuit of the relays 94 and 89 at contact 8 of relay 88. The tip relay 'TR ict iia

of the trunk circuit C is also denergized due to the replacing of the receiver at called substation Gr. The opening of contact of relay TR opens the energizing circuit of relay CT of cord B which again brings about ,the lighting of' the supervisory signal SS1,

notifying the operator at B thatthe conversation has been terminated. The circuit for the release magnet RM and the side switch release magnet SM, is not as yet-closed due to the fact that relay 74 is still held energized from battery through the sleeve relay SR at the trunk circuit C. The operator through the winding of the said magnet RM,

conductor 99, alternate contact 100 of offnormal contact ON1, normal contact 101 of relay 54, and normal contact 102 of relay 94 to ground at normal contact 103 of relay 74. The circuit of magnet SM extends from battery through the winding of said magnet, conductor 99, following the same path as lthat of magnet RM. The magnet RM, upon energizing, releases the wipers 7, 8, 9, allowing them to restore to normal and the magnet SM upon energizing, releases the side switch to normal or first position. The offnormal contacts ON1 are also restored to normal thus opening the circuit of the release magnet RM and side switch release 4magnet SM, the two magnets restoring to normal. The apparatus at the connector E is now at normal and is available for estabhshing other connections.

Upon the removal of the plug TP from the jack TJ1, the circuit of the relay SR of 'the trunk circuit C is opened bringing about the denergization of the relay IN. The

- operator at B having received the disconneet signal from the subscriber at A, due to the denergization of the relay AT, removes plugs AP and GP from their respective jacks, the removal of plug AP opens the circuit of relay CO of L and AS of the the cord circuit B and the removal of the plug CP from the -jack'TJ denergizes the relay CS of the cord circuit B and also the relay TC. ofthe trunk circuit C. The apparatus now returns to normal and the cord circuit B, trunk C, impulse machine D and connector E are now available for other connections. V

Referring now to the guard relay GR, of the trunk C. This relay is used as a guard against interference on the impulse Wire when a connection is being set up 'while the impulse machine is still running. Tn this event should the impulse machine be still running while the trunk plug TP of a trunk -circult as C be inserted into a trunk jack as TJ1` leading tol afconnector E, a circuit for the guardv relay GR will be'immediately. establlshed, the circuit being traced from battery through the alternate contact 112 of relay AC of circuit D, (the said relay AC being held energized during the-operation of the impulse mechanism due to its being a `slow-acting relay), the Winding ofrelay GR, the make-before-break contact 113 of relay RS, the closed contacts of. the depressed ringing -plunger of the ringing key RK,

(Which is depressed 'by the operator after energizing, and the connection of the im-v pulse lead through the alternate contact 42 of the relay 4IC to the tip conductor of the trunk circuit C. With this relay GR `provided, it is impossible to interfere with the impulses While they are being transmitted to a connector' E.

Now let us assume that the ycalled automatic subscribers line is busy, the operation of the circuit is the same as previously described up to and including the time that the side switch is stepped to second position to engage the contacts 70, 71, 72 and 73. The called subscribers line being busy, a ground will be encountered by the private wiper 7 in engaging the private contact 10 of `the lcalled line contacts, the said ground being furnished by anotherswitch already in use. The relay PR denergizes as before after the group of impulses have been transmitted and opens the contact 51 bringing about the restoration of the relay 50. The side switch relay SW is energized as before through the normal contact 67 of relay 50 to ground, the relay SW stepping the side switches a, b, c, and d, into their second orfinal position.

second'or linal position opens the energizing circuit for the slightly slow-acting relay 54. The relay 53 has its circuit interrupted due to the opening of the contact 52 of relay 50, the relay 53 also being slightly slow-acting, and a substitute circuit for the said relay is established before it restores. The said circuit being traced from battery through the winding of the relay 53, conductor 55, normal contact 52 of relay 50, conductor 120, alternate contact 121 of said relay 53, conductor 122, conductor 123 to the ground encountered by the private wiper 7. rPhe side switch relay SW is therefore held energized,

the circuit being traced from battery through the winding of the said/relay, conductor 63, alternate contact 64, conductor 124, alternate contact 125 of relay 53 to ground at normal contact 126 of relay 54. The relay 74 is energized as soon as the side switch yhas moved to its second position, the

vThe switch Wiper 57 having stepped to its restoration of the other connected 'is the same as before described.

y circuit extending from ground through the upper winding of the relay 74, contact 72, wiper 69 of side switch c, sleeve contacts of the Connected plug and jack, normal contact 77 through winding of relay SR of trunk circuit C to battery. Upon the energization of the relay 74 the tone generator T0 is started, the circuit being traced from battery through tone generator TC, alternate contact 127, of relay SW to ground at alternate contact 103 of relay 74. The busy back machine is now connected to the calling line over a circuit traced from battery through busy back BB, alternate contact 128 of relay SW, alternate contact 84 of relay 53, make before break contact 91 of relay 89, Contact 71, wiper 68, the tip contacts of the connected plugV and jack, normal contact 42 of relayIC, alternate contact 90 of relay SR, through the winding of relay TR to ground, the busy signal also being transmitted to the calling subscriber notifying him that the' called line is busy. The relay TRof the trunk circuit C is thus intermittently operated due to the busy back machine. The intermittent operation of relay TR causes the `supervisory relay CT to ash the supervisory signal SSf The operator noting the flashing supervisory si nal knows that the called line is busy an removes the plug CP from the trunk jack TJ. The removal of the plug CP from the jack TJ causesthe supervisory signal 20 to be operated. The operator at C noting the glowing of the supervisory signal 20 removes the trunk plug TP from the trunk jack TJ1. The removal of the trunk plug from the trunk jack opens the energizing circuit of relay 74, the relay 74 denergizes and closes a circuit'for the release magnet RM and the side switch release, magnet SM as beforev described. The two relays upon ener izing bring about the restoration of wipers 8 and 9 of connector switch E, and the side switches a, b, c and d. The

apparatus Referring now to Fig. 2, T here show the construction of the strip of keys K which are associated with the impulse machine D, the key-board comprises 'an escutcheon 130 to which, by suitable means the studs 131 and 132, an insulating plate' 133 is held in place by means of the plate 134. The insulation plate carries suitable spring combinations, ccm rising normally closed contacts 135 and|137 and normally open contacts 136 and 138, which vare adapted to be actuated by means of thednsulating buttons 139 carried by a plunger rod 140. The plunger rod ,is mounted at one end in the 'escutcheon plate 130 and at the other end in the insulation plate 134. A suitable spring 141 tends to hold the plunger in its upper position. The-plunger is provided with a cam 142 its indicating position after it is depressed,

and to this end I provide a sliding plate 143 which slides transversely of the frame work, the said plate being suitably supported between the studs 131and 132. .The plate has a plurality of cam openings 144 with which the cams 142 coperate.

Assuming now that a plunger is depressed to its fully depressed position, in its downward movement the cam 142 engages the caln surface of the opening 144 of the plate 143. The plate 143 is forced to the right against the tension of the leaf spring` 145, when the upper surface of the cam 142 passes below the bottom surface of the plate 143, the said plate is forced back to its non mal position by means of the leaf spring 145. When fully depressed, the insulating button 139 engages the contact springs 135 and 136 opening normally closed contacts -135 and 137 and closing normally open conspring 141 forces the plunger up until the cam engagesthe bottom surface of the plate 143. In this position the contact springs 135 and 137 are held open due to the said spring 135still engaging the angular surface of the button 139. The spring 136 being shorter than the spring 135 restores after the key is moved to its indicating posi'- tion again engaging its spring contacts 138. Thus in indica-ting position, the contact springs 135 and 137 are open and springs 136 and 138 are allowed to Krestore to again close their contacts. To release a depressed key plunger from indicating position, I provide a key releasemagnet KM suitably connected to theescu-tcheon plate 130. The said magnet, upon energizing attracts its armature 146 and through the medium of its eXtension`1461 which carries a rubber buffer 147 that engages the plate 143 moves the plate 143 to the right until the opening 144 of the plate 143 allows the plunger to restore to normal. The leaf spring 145 moving the plate 143 to the left to normal after the magnet has denergized.

In practising my invention, it will be apparent that many alterations and modifications may be made not only in the mechanical construction of the various elements entering into the system, but also in many of the circuit arrangements, Without departing from the spirit and scope'of my invention. Therefore I have sought to use such terms in the appended claims as will fully cover matic switch having access to the lines 4in one of said groupspof lines, a step-by-step motor magnet for saidA automatic switch, link circuits, an operators calling device associated with said link circuits, keys for! `said' calling device equal in numbe-r to the number of subscribers lines in one of said groups of lines, means 'for operatively connecting said calling device with said automatic switch through the medium of one of said link circuits, and impulse generating means lncluded 1n sald calling device and controlled by one of said keys for transmitting impulses to the said step-by-step motor magnet of said automatic lswitch to extend a connection to a called one of said lines.

2. A ytelephone system comprising subscribers lines divided into groups, automatic switches for connection with said lines, operatorsnlink circuits provided'wi'th frequency selecting devices, a calling device associated with said link circuits, means responsive to the operation of one of said Jfrequency selecting devices for connecting said calling device to one of said link circuits,

and means responsive to the operation of said calling device for operating one of said aurso tomatic switches to extend a connection tol one of said lines.

3. A telephone system comprising suby scribers lines divided into` groups, an automaticswitch having access to only the l'ines in one of said groups of lines, astep-by-step motor device for said automatic switch, a plurality of trunk circuits, an operators calling device associated with said trunk circuits, means for connecting said calling de- Alli l automatic `switches are adapted to operate.

scribers Ilines divided linto groups, auto-v matic switches for extending connections to said lines, motor devices for said automatic switches, a plurality of trunk circuits, an operators calling device associated with said trunk circuits, means for connecting .said calling device to one of said automatic switches .through one of said trunk circuits,

'60 keys for said calling device equal innumber to the number of subscribers lines) in a group and to the number of steps `said and means controlled by the operation any one of said keys to transmlt operating lmpulses to the motor device of said conimpulse-sending device nected switch to move the wipers of said connected switch into engagement with any one of the lines in .one of the said groups of lines.

5. Anv impulse-sending device for -con- 4trolling p a step-by-step automatic switch,

keys forsaid device equal in number to the number of steps that said switch is adapted to operate, bank contacts equal in number to the number of said' keys, normally closed connections extending from said keys to the said bank contacts, .and means controlled by the depression of one of said keys for opening one of said 'normally closed connections thereby controlling the number of steps that said switchwill operate.

6. An impulse-sending device comprising bank contacts and a wiper .for coperation therewith, an automatic switch adapted to be controlled by said impulse-sending device, keys equal in number to the maximum` number of steps that said switch may operate, connections from the said keys to the said bank contacts, means controlled yby the said keys for ali'ecting the said connections thereby controlling said automatic switch.

7. A step-by-step impulse-sending device provided with a single roup' of keys, a 'stepby-ste automatic switc adapted to be-connectedp to said impulse sending device, a driving magnet for said step-b -step automatic switch, means controlled y the operation of one of said keysl for causing said impulse sending device to step forward, and means for transmitting impulses to said motor magnet to cause said automatic switchi to take a number of steps equal in number to the steps taken by said impulse sending device, andmeans `for releasing said impulse sending device without aifecting the' operative position of said automatic switch.

8. A step-by-step impulse-sending device rovided with a single group ofv controlling eys, an automatic connector switch adapted .to be connected to said device, the keys of said device being equal in number to the llt) maximum, number of steps that said device is adapted to operate, means controlled by said keys for stepping the said device ahead, and means for operating said connector switch -a corresponding' number of SPS- 9. .In I a telephone system, subscribers .lines divided into groups, a step-by-step connector switch forA connection-to any one of the lines in one of said 'groups of lines and to no 'other lines, a step-by-step iml pulse-sending device for controlling said connector switch, keys for said impulsesending device equal in number to the number of lines in one of said groups and vto the number. of steps said connected switch is adated to take, and means controlled by sai keys for simultaneousl operating said said connector its corresponding bank contact and for initiating the operation of Said motor mechanism, and means controlled by the engagement of said wiper with the said bank contact to prevent further operations of the said motor mechanism and for restoring the said wiper to normal. Y

l1. A calling device comprising a plurality of bank contacts and a wiper for cooper-ation therewith, a motor mechanism for driving said wiper over said bank contacts, a plurality of keys equal in number to the number of bank contacts, connections between said keys and said bank contacts, means controlled 'by the operation of one of said keys for affecting the electrical condition of its corresponding bank contact, and means controlled by the engagement of said wiper with said bank contact for preventing further operation of said motor mechanism and vforrestoring said key to normal. l2. A calling device comprising a plurality' of bank contacts and a wiper for cooperation therewith, motor mechanism Jfor driving said wiper over said bank contacts, a plurality of keys equal in number to the number of bank contacts, connections between said keys and said bank contacts, means controlled by the operation of one of said keys for aii'ectin the electrical condition of its correspon ing bank contact, and means controlled by the engagement of said wiper with said bank contact for restoring the electrical condition of said contact.

13. In a telephone system, an operators link circuit provided with a calling device and a frequency selecting device, an automatic switch .for extending connections to called subscribers lines, means controlled by said frequency selecting device for selecting the desired fre uency to signal the called subscriber' and or connecting said calling device to said automatic switch, means for operating said calling device whereby said switch is operated to extend connection to a called subscribers line, and means operated upon the connectionpf said switch to said called line for applying the selected ringing current to the said called line.

14. En a telephone system, a plurality of 5 operators link circuits provided with frequency selecting devices, a calling device associated with said link circuits, automatic means for extending connections'to called subscribers lines, means for operating said frequency selecting device to select the desired ringing current to signal a called subscriber and for connecting the said calling device to said automatic means, and means Vfor delaying the application ofsaid selected ringing current to the called line until said automatic means has extended connection to the said called subscribers line.

15. In a telephone system a plurality of operators link circuits, a calling device associated with said link circuits, a relay in each of said link circuits, means for connecting saidcalling device to one of said link circuits, means for 'operating said calling device, and means controlled by the operation of said calling device for energizing the relay of a second of said link circuits to prevent its connection to said calling device.

16. A telephone system comprising-a calling subscribers and a called subscribers line, means including an A-operators link circuit, a B-operators link 4circuit and an automatic switch for connecting said lines, an automatic machine-controlled impulse sending device for controlling said switch,

a supervisory signal for 'said A-operators link circuit operated upon completion of the connection to the called subscribers line, and means for intermittently operating said supervisory signal upon the completion of said connection, if said called subscribers line tests busy.

17 In a'telephone system, a plurality ofV subscribers lines arranged in a group, a' step-by-step switch for connection to only the lines in said roup of lines, a step-bystep impulse sending device provided with a plurality of keys substantially equal in number to the number of steps said switch is adapted to o erate, means controlled .by the operation ofp one of said keys for operating said impulse sending device and said automatic switch, and means for synchronizing. the operations of said impulse sending device and said automatic switch.

18. In a telephone system, a plurality 'of operators link circuits, a calling device associated with said link circuits, key controlled means for connecting said calhng def vice to one of said link circuits, and means for preventing the said calling device from' number of subscribers lines in any one l group, automatic switches for each group of said s hscribers lines, trunk lines asseciatcd with said impulse sending device and git@ terminating in said automatic switches, and means for connecting said impulse-sending device to one of said trunkcircuits and for operating a single one of said keys whereby one of said automatic switches is operated to extend a connection to a called one of said lines.

20. A telephone system including subscribers lines divided into groups, automatic switches divided into groups corresponding to the number of groups of subscribers lines, anA operators board and a B operators board, trunk lines extending from said B operators board to said automatic switches, an impulse-sending device at said B operators board provided withkeys, means for extending a call from a calling line of one of said groups to said B operators board,

land means controlled by the B operator for extending a call via one of said trunks to one of said automatic switches and for operating one of said keys whereby said automatic switch is operated to extend a connection to a called line in one of said groups.

21. A telephone system. including subscribers lines divided into groups, automatic switches divided into groups corresponding to the number of groups of subscribers lines, an A operators board and a B operators board, trunk lines extending from said B operators board to said automatic switches, an impulse-sending device at said B operators board provided with keys, one for each subscribers line in a group, means for extending a call from a calling line of one of said groups `to said B operators board, and means controlled by the B operator for extending a callvia one of said trunks to one of said automatic switches and for operating one of said keys whereby said automatic device and said switch to complete a connection with the desired one of said lines.

23. A telephone system `including a group of subscribers lines, a step-by-step' automatic connector switch adapted to make con.

nection with any one of said lines, a stepby-step calling device for controlling said automatic switch, said calling device being provided with as many keys as subscribers lines in the group and adapted to operate as many steps as the automatic switch is adapted to operate, a link circuit, a selective ringing key, means including-said link circuit and said selective ringing key' for operatively associating said calling device with said automatic switch, andmeans controlled by one of said keys for operating said calling device and said switch to complete a connection with the desired one of said lines.

Signed by me at Indianapolis in the county of Marion and State of Indiana, in

the presence of two witnesses.

HARRY W. MUNSELL. 

